Method of producing welded molybdenum



Uflittid States Patent 2,698,892 Patented Jan. 4, 1955 lybdenum sheet generally contains in the. neighborhood $698392? of 0.005% cargo; and in all cgses does notfctantain mare than a out-t 1 0.63.1 on... ttempts to a ricate: is METHOD OF PRODUCING'-WELDED" commercia-lzimolybdenum. by. butt welding results in: a MOLYBDENUM 5 cracking. 0f.;the 1yveld upon cooling. and the crack follows t e progress of t e arc. C r 1 o r :t ih: lhg1 -a gh gg f flifi zg gggk olybdenum sheet formed from ingots or bars prepared of New York rom a mixture of molybdenum powder and small and limited amounts of finely divided carbon may be satis- N Drawing, Application December 29, 1950, factorllyfabrlcated by butt welding in an nert atmosphere serial 203,547 e molybdenum sheet for such fabrlcatlon contains from about 0.02% to about 0.09% total combined carbon, pref- 1 Claim. (Cl. 219-10) erably from about 0.03% to about 0.0 Fabrication of molybdenum sheet containing combined carbon within This invention relates to a weldable molybdenum and this range may be satisfactorily effected by butt welding method of preparing the same so that the molybdenum 1s I 0 eneounterlng the normal cracking of the Weld susceptible to arc welding to provide crack-free butt upon cooling. In preparing the mixture of molybdenum welded joints. powder and finely divided carbon, the amount of carbon Molybdenum, because of its refractory nature, cannot a e m s e sufficient to P e the g t o bar With be prepared by common metallurgical smelting practices the required a t f ar nan is conventionally prepared b powder metallurgy The r n y be in rp ra in h molybdenum methods and by a vacuum arc casting method. In the by adding the carbon to h molybdenum p r i h conventional powder metallurgy method, powdered molybform of finely divided carbon Such as p black- The denum is pressed in a die and the pressed bar then sintered powdeljs f thoroughly and intimately mixed as y a in hydrogen or in a vacuum. The bar or ingot thus prel mflhng Operatione p fi amount of Carbon pared i li i d i i I h vacuum are casting which 1s added to and mixed with the molybdenum powder method, the molybdenum powder is pressed into a bar w1l1 be dependent upon the amount of carbon desired in and the pressed bar employed as an electrode This pressed the lnget e finlshed Sheet- 111 all cases the amount of bar ecomes melted n a vacuum By th s vacuum castcarbon V VhICh 18 added 110 thfi molybdenum powder should ing, somewhat larger ingots may be obtained However, be sufficient to provide the molybdenum sheet with from this method also produces ingots or bars of a relatlvely about 092% to aboht 0 E combined carbohll slze as compared to ingots hi h may be for d It appears that durlng the welding operation, the carbon f th more commonly d metals Th b ingots rnust be present in the molten metal or must be released produced b powder metallurgy methods and by thc m the molten metal in the form of elemental or atomlc vacuum casting method are subsequently mechanically In Order 1 61111111121156 cl'acklng Q j Weld P P worked as by rolling to produce sheet molybdenum The coohhg- In addlhg carbon as hhely dlvlded carbon, It size of molybdenum sheet is necessarily limited because hecomhs h l' by ohl'eacts Wlth the molybdenum of the limited size of the initial bars or ingots. 6 slhtenhg Operahoh to form sohlhon of carbon Because of the refractory nature of the metal, its use 40 In the molyhdehhm molybdenum Carblde- During the or various hlgh temperature applications highly desir. welding operation the carbon ls apparently released from able The fabrlcatlon of various structural shapes has the Soluhoh or molybdenum carhlde E 15 free to react been deterred because of the inability to weld molybdenum Wlth Oxygen other ents which normally cause to form the desired shape or to form larger sheets of the crackles of the Weld metal h coohhg Thls i L Because f h high ffi it f molybdenum f M explanation 1s merely set forth as a possible theory because oxygen, some f h commonly used welding methods are the presence of carbon as free carbon does not ellmlnate necessarily excluded. The use of inert atmospheres must the cracklhg of the Weld Theta! h coohhgbe employed to protect molybdenum from oxygen con- Molybdhhum bars lhgots, for example, h he Ph i atmospheres pared by powder metallurgy methods. An lntlmate mm- It has been impossible to fabricate molybdenum by the ture, of molybdenum, powder and carbon is formed by usual arc welding techniques although by inert gas welding adding the finely chvlded carbon such as lamp black or techniques the molybdenum may be satisfactorily pro- P graphlte t0 h molybdenum powder and subtected from oxidation. The weld produced is brittle and lechhg the mixture to a ban hhhlhg P The the weld cracks upon cooling For example, m the weld addition of about 0 1% carbon to the molybdenum powder mg f molybdenum sheet, the edges of the molybdenum rr Wlll result ln the productlon of finished sheet containing are placed in abutting relationship and held in such posl- M between about 0 025% and about 0 03% comblhed carbon tion by mechanical means. e area immediately over- After thoroughly hhxlhg F molybdenum powder and lying the electrode is supplied wlth the inert gas and an h a the powdel: mlxhlre 1S Placed In a desll'ed (he and are ll'lltlated between the electrode and the abuttlng edges subleoted to sufiiolent pressure to f m l pp e electrode is then advanced along the abuttlng edges bars hlllets The bars billets are Subsequently or the sheet is moved with respect to a fixed electrode sintered in a hydrogen atmosph r The resulting y The Weld thus produced is always brittle Invariably the denum ingot or bar is then mechanically worked in accordmetal which has been melted cracks upon cooling and ance with conventional practices to produce sheet form of the crack follows the progress of the arc. the desired thickness. The sheet form molybdenum con- PI'lHClDal purpose of the present ln e lon Is to 5 taining the combined carbon is fabricated into large sheet lpglyllgggamtgeglgdmzfv iilggfc a i dgzi y 50 that the iorm or lingoddesired shapes by placmg edges of the sheet A further obiect of this invention is to provide a new 35 23 h i figo s l'l cg' s li fh i by molvbdenum product which is readily susceptible to arc erabl b the us m t as ig e mm fa welding in an inert atmosphere with such welds free from 7 electridey e a ngs en or 0 er men we mg crzgks after the joint has been cooled. I

ther objects and advantages of this invention will The me'thod of produclng fabricated molybdenum char- ?gfigg: apparent from the descnpnon and clam whlch acterized by crack-free butt welds which comprises the Ihave discovered that molybdenum may be butt welded Steps of fonmng mgot molybdenum from an mhmate if the sheet molybdenum has been produced from molybmlxture of molybdenum Powder and a Small amount of denum powder to which has been added certain small and added chrbon F amount of added harboh helhg Suhlcleht limited amounts f carbon to provide the ingot molybdenum with from about 0.02% As stated hereinbefore, there has been no method to about carbon mechanically Working the ingot known whereby conventional molybdenum sheet can be so moly d Into sheet form molybdenum, p t ning fabricated by a welding method. Commercial grade moedges of such sheet form molybdenum in abutting relai 4 OTHER REFERENCES tionship and arc welding the abutting edges in the presence of an atmosphere Park et aL, pages 1-12 of The Melting of Molybdenum in the Vacuum Arc, American Institute of Mining an hnical Publication No. 2052 References Cited in the file of this patent 5 Metallurgical Engineers Tee UNITED STATES PATENTS infl45ials 'giihliloggy,S62:.C?Iber11%4g. l 75 N 1,054,005 Lederer Feb. 25, 1913 at, Y n 1 605 07 Ronci Nov 2 1926 21, 1949, Pages 2,491,866 Kurtz Dec. 20, 1949 

